My son has a dv2310us (running vista). He had the same problem. We ended up sending back to HP. If I remember correctly, they had to replace the motherboard.
Sorry to say, this model of laptop had many problems. He had a different issue with it nearly one year after we bought for him. We sent it to HP, and it took them nearly 2 months to get it back. When I called for status, they told me the parts were back-ordered due to high demand, becasue many laptops were having the same problem.
We got lucky because HP extended the warranty by a year. Towards the end of that period is when he had the problem you mention.
Sorry to be the bearer of bad news...